This invention relates to emulsion polymerization processes. Such processes are normally exothermic, and in many cases, it is difficult to remove enough heat from the reaction vessel to prevent the contents of the reaction vessel from reaching undesirably high temperatures such as, for example, temperatures of 100° C. or higher. In many cases, transfer of heat through the walls of the reaction vessel does not remove enough heat from the contents of the reaction vessel to keep the temperature of the contents of the reaction vessel desirably low.
One effective method of removing heat from the contents of the reaction vessel is passing a portion of the contents of the reaction vessel through a recirculating loop that contains a heat exchanger. For example, U.S. Pat. No. 6,3200,000 describes a process for preparing polymer that includes pumping the polymer through an external loop.
One difficulty with such external recirculating loops is that they are prone to imparting shear to the material being passed through them, and the shear can cause emulsion polymers to coagulate. Some emulsion polymers are more susceptible to coagulation than others. It is desired to provide a process for emulsion polymerization that provides effective cooling and that has a reduced tendency to cause emulsion polymers to coagulate.